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Idiomas disponibles
Idiomas disponibles
2. Description
The Franck-Hertz control unit can be used
to operate the mercury filled Franck-Hertz tube,
the neon filled Franck-Hertz tube or the critical
potential tubes S. It provides all the voltages
needed to power the tubes and includes a highly
sensitive built-in DC amplifier for measuring col-
lector current.
1. Accelerating voltage U
Choice of 0 − 80 V stabilised DC voltage
("Man(ual)" mode) or 50 Hz saw-tooth voltage
("Ramp mode"). At the oscilloscope output U
this voltage is divided by 10.
2. Heater voltage U
:
F
DC voltage 0 − 12 V for the heater filament of the tube.
3. Countervoltage U
:
E
DC voltage of 0 − 12 V for reverse bias between
grid and collector electrode.
4. Control voltage U
:
G
DC voltage of 0 − 12 V between the control grid
and the cathode in the neon-filled Franck-Hertz
tube
5. DC amplifier:
The DC amplifier provides a voltage proportional
to the collector current, rated up to 10 mA. At the
lowest amplification 1 V of voltage measured
corresponds to an electron current of 38 nA
approx. and at the highest amplification to an
electron current of 12 nA approx.
The voltages can simultaneously be read off a
display.
Additional measuring inputs are also available for
the anode current and accelerating voltage.
The apparatus 1012818 is for operation with a
mains voltage of 115 V (±10%), and the unit
1012819 is for operation with a mains voltage of
230 V (±10%).
3. Technical data
Mains voltage:
Filament voltage U
:
F
Heater current:
Control voltage U
:
G
Accelerating voltage U
Countervoltage U
:
E
Output U
for
Y
collector current I
:
E
Output U
for
X
accelerating voltage U
Outputs:
Input:
Dimensions:
Weight:
:
A
See back of chassis
0 − 12 V, continuously
adjustable
0 − 2.5 A
0 − 12 V, continuously
adjustable
: 0 − 80 V, continuously
A
adjustable
or
tooth
0 − ±12 V, continu-
ously
adjustable,
switchable polarity
= U
*38 nA/V (0−12V)
I
E
A
:
= U
/ 10
U
A
X
A
4 mm safety sockets
BNC socket
3
160x132x210 mm
approx.
3.4 kg approx.
4.1 Franck-Hertz tube with Hg filling
Additionally required:
1 F/H tube w. Hg filling a. heating chamber (230 V,
50/60 Hz)
or
1 F/H tube w. Hg filling a. heating chamber (115 V,
50/60 Hz)
1 Analogue oscilloscope, 2x 30 MHz
1 HF patch cord, 1 m
2 HF patch cords, BNC / 4-mm plug
X
Safety leads for experiments
•
Place front plate of the open side of the heat-
ing chamber and fix it in place with 6 knurled
screws.
•
Turn off the heating chamber and the control
unit to begin with and turn all the knobs on
the control fully to the left.
•
Do not apply a voltage to the tube when it is
still cold (the mercury inside may cause a
short circuit).
•
Connect terminals "A", "F" and "K" (refer to Fig.
1).
•
Connect terminal "E" of the Franck-Hertz
tube to the correct input on the control unit by
means of an BNC cable.
•
Connect the "FH Signal U
the control unit to the Y input of the oscillo-
scope and terminal "U
•
Turn on the heating chamber. Set a tempera-
ture of about 210° C and wait for the tube to
warm up (about 5 to 10 minutes).
•
Turn on the control unit and the equipment
should enter ramp mode.
•
Set a filament voltage of 6 − 7 V. The indi-
rectly heated cathode requires about 90 sec-
onds to warm up, once the voltage is applied.
•
Set the minimum acceleration voltage to
zero, slowly increase the maximum accelera-
tion voltage to 80 V.
•
Do not, however, increase the accelerating
voltage so much that self-discharge no longer
occurs inside the tube. Any ionisation due to
collisions will disrupt the curve.
•
Set up the oscilloscope initially with settings
of x = 1 V/div and y = 1 V/div.
saw-
•
Observe the emergence of the maxima in the
Franck-Hertz
screen.
•
Set up all the parameters, accelerating volt-
age, cathode filament, bias voltage and am-
plitude so that a trace with nicely delineated
maxima and minima is obtained.
The procedure as described so far is a general
setting procedure. Since the Franck-Hertz tubes
are hand-made, there may be quite large differ-
ences in the optimum parameters from one tube
to the next. The test report included with the tube
should give some idea of where good results may
be obtained for the tube in question.
2
4. Examples of use
-out" terminal of
Y
" to the X input.
X
trace
on
the
1006795
1006794
1002727
1002746
1002748
oscilloscope
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